Hi guys. I used to have a Denon receiver which didn't offer much in the way of adjusting subwoofer level. So after running Audyssey my VTF-15h was set at the 9:00 position. Perfect for music, but I bumped it up to 10:30 or 11:00 for movies. Again, everything sounded perfect. This was about four years ago.
Now I just bought a second VTF-15h MK2 (my wife says I don't need it and she's probably right, lol). I also now have a Marantz AV7703, which offers several options for boosting subwoofer input levels. After running Audyssey with the subs at the 9:00 position, sub1 (the older unit) was at -11 and sub2 (the new one) was at -5. This didn't seem like enough bass for me, so I bumped them up to -6 and 0, respectively, in the Audyssey settings. Also, the newer sub had more trouble "waking up", so I went to the subwoofer input level in the Marantz settings and bumped it up +3. This worked. So far so good. The AV7703 also allows adjusting levels of all speakers, including subwoofers "on the fly." The current settings are great for music, I usually adjust between 0 and -5 depending on the source. So much difference in mastering and remastering these days.
My question is about getting more for punch for movies. After reading about distortion/clipping and especially damage to the driver, I worry about how much I can bump up the input from the controller, as I have already done so from the original settings. Would it be safe to go as high as, say +10? I worry about going into the positive numbers so much, or would it be better to increase the volume at the sub itself? Or would this increase the chance of clipping and possible damage to the driver, since the Audyssey setting was at 9:00.? I know the golden rule is set the volume and don't touch it again! I never had trouble doing it that way before I started learning more about how levels and gains worked. I just haven't learned enough. I guess ignorance is bliss! as the saying goes.

Yea that's a very tough question because it's dependent on so many different variables. I'll put it this way, let's say you play a 50 Hz test tone at your listening position at 85 dB. You go to the receiver and turn down the channel level by 5 dB and you turn up the sub gain 5 dB, the effect on the amp and driver will still be the same. So it ultimately depends on how loud you want the sub to play. However, another possibility is if you use too high of a channel level setting on the sub, it could potentially the output stage of the sub line level output and that may cause more compression/distortion. It really depends on how denon designed it. I'm fairly sure that going up to +5 or something probably isn't that big of a deal but going up to +12 or +10, it might be? It's hard to say. One thing to note is that we did make the gain control less sensitive from the mk1 to the mk2, so that explains the volume difference there. So generally I would say you can run upwards to 11-12 o'clock with no problems, but again that depends on the input voltage going to the sub. You generally should not have to set it higher than 1 o'clock. That may raise some concern.

Thanks for the advice. I never needed to set the single sub above 11 o' clock, so I'm sure I won't have to with two. I never like to go too far in the positives for subwoofer level input or above 12 o' clock on the unit. These great subs give all I could ever want at reasonably low levels. And I want to add that the VTF-15h is the best value I have ever spent my money on for electronics, or probably anything else, for that matter. Thanks Dr. Hsu!

I realize these posts are rather old, but I thought I'd share some knowledge I have of the processing in the Denon/Marantz products.

My direct experience is with the Denon 3313CI (a 2013 product), but AFAICT, most recent Denon and Marantz products are similar.

The short of it is that for the best performance I recommend setting up the system so that the sub level in the AVR is as low as possible without going below the limit of "-12". Practically speaking, aiming for "-10" (at the most) is probably completely reasonable, and even much higher settings will be OK "most of the time". See below.

In more detail: With Audyssey off (*), the AVR appears to be designed so that a hypothetical 7.1 channel soundtrack in which sub bass is playing at maximum level ("digital full-scale") on all of the channels at the same time will be output cleanly by the AVR if the sum of the master volume and sub level are less than -12. If either the master volume or sub level add up to to a number greater than -12, then it is *theoretically possible* for the bass from a 7.1 channel soundtrack to overload the subwoofer output. So for example, if you don't ever listen higher than "-6" on the master volume, then a sub level of "-6" would be OK, but you need "-12" to not overload if you sometimes turn up to "0".

(*) BUT! If Audyssey is running, things get a lot more complicated and overload is possible at *much lower levels*. Audyssey can boost the signal quite a bit. How much precisely is very complicated, especially if Dynamic EQ is enabled. In other words, it's a good idea to setup the system with the sub level as low as possible if Audyssey is being used, even if the volume is kept fairly moderate. That way you get as much capability out of the subs as possible before they overload, and when they overload, they will do so much more gracefully than when the AVR output overloads.

As far as actual movie content is concerned, I'm not aware of any soundtracks that play bass at maximum ("digital full-scale") level on all channels at the same time, but a few get within a couple dB. Lots more get within 6 dB of the max.

I can't speak for other AVR/processor manufacturer except to say that every product has limits and some designs are more flexible about getting around those limits than others. Unfortunately, information about this sort of thing is scarce, even at places like AVSForum. I figured out the limits of my Denon with careful testing and found corroboration for my findings in other products elsewhere. It's a shame these details aren't well documented by the manufacturers because they are crucial to optimizing a high performance system.

Trust me, this is a bigger deal than most people realize. I bet a lot of sub capability goes to waste simply because people are overloading in an AVR or processor.

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